1. Field of the Invention
The invention relates to thermoplastic polyurethane (TPU) composites. In one aspect the invention relates to TPU composites that are halogen-free and flame retardant (HFFR) while in another aspect, the invention relates to TPU composites that are halogen-free, flame retardant and comprise tris(2-butoxyethyl)phosphate (TBEP) or its oligomer, an organic phosphate ester and a metal hydrate.
2. Description of the Related Art
TPU elastomers can have a broad range of flexibility. They can be fabricated by a wide variety of methods from injection molding to extrusion to blow molding. They also offer performance benefits of clarity, abrasion resistance, chemical and hydrocarbon resistance, and load-bearing and tensile strength. Accordingly, they cover many applications which require flame retardancy.
The traditional flame retardants used in TPU compositions are halogen-based, i.e., they contain bromine, chlorine etc. However, due to the ever present concerns for the environment and safety, halogen-free flame retardants are now favored but these can pose a challenge for TPU compositions. Conventional and readily available halogen-free flame retardants, e.g., those based on organic phosphates such as resorcinol bis(diphenyl phosphate) (RDP) and bisphenol-A bis(diphenyl phosphate) (BPADP), do not produce a flame retardant TPU composition that exhibits good smoke suppression. Of continuing interest to the TPU industry is a halogen-free TPU composition that exhibits both good smoke suppression and flame retardancy.